Alkylbenzenes, oxidation side-chain substitution

Alkyl-substituted benzenes are oxidized both on the benzene ring and on the side chain. Additionally, some dimerization occurs.36 Alkylbenzenes containing linear alkyl groups are oxidized preferentially at the side chain33 nearest the benzene ring for example, ethylbenzene oxidizes first to 1-phenyl ethanol and then to acetophenone.36... 

The most important reactions of the alkylbenzenes are outlined below, with toluene anti ethylbenzene as specific examples essentially the same behavior is shown by compounds bearing other side chains. Except for hydrogenation and oxidation, these reactions involve either electrophilic substitution in the aromatic ring or free-radical substitution in the aliphatic side chain. 

Solution N-propylbenzene is a compound made up of aromatic and alkane units. Hence, it belongs in the category of alkylbenzenes, which, in turn, are part of the group of compounds known as arenes (compounds that contain both aliphatic and aromatic units). Such compounds show two sets of chemical properties. The ring undergoes the electrophilic substitution characteristic of benzene, whereas the side chain undergoes the free-radical substitution characteristic of alkanes. Each should modify the other. Except for oxidation and hydrogenation these are the reactions to be expected for arenes. 

While the side-chain deprotonation of radical cations prevails for alkylbenzenes, for polycyclic aromatics, attack by nucleophiles can dominate [35b, 37, 38], resulting in oxidative nucleophilic substitution (Scheme 14.6). 

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